1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive correcting a track address during a write operation.
2. Description of the Prior Art
Disk drives for computer systems typically comprise a disk rotated by a spindle motor with a head actuated over the disk in order to access data recorded in concentric tracks. The head is coupled to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) in order to seek the head to a target track, and then maintain the head over the track (tracking) while performing read or write operations. The position information for servoing the head comes from servo sectors recorded at periodic intervals around the circumference of the tracks. The servo sectors typically comprise coarse position information in the form of a digital track address, and fine position information in the form of servo bursts recorded at precise offsets relative to the centerline of each track.
FIG. 1 shows a prior art format of a disk 2 comprising a plurality of concentric tracks 4 having embedded servo sectors 60-6N. Each servo sector (e.g., servo sector 64) comprises a preamble 8 for synchronizing gain control and timing recovery, a sync mark 10 for synchronizing to a data field 12 comprising the coarse head positioning information (such as a digital track address), and servo bursts 14 which provide fine head positioning information. If during a write operation the track address detected from the read signal does not match the track address of the target track, the write operation is typically aborted so that data is not written on the wrong track. After aborting the write operation, the control circuitry will typically “slip” a revolution and attempt to re-execute the write operation.
In some cases, during a write operation the head may actually be over the correct target track but the wrong track address is detected from the read signal due to a detection error (due, for example, to an insufficient signal to noise ratio) rather than from the head being over the wrong track. Aborting the write operation in these cases decreases the throughput of the disk drive due to the latency caused by slipping revolutions and re-executing the write operations.
There is, therefore, a need to increase the throughput of a disk drive by reducing the number of aborted write operations.